Size and not the chemical feature of the amino acid side chain at position 67 is critical for increased geranylation activity of MnmH.

ND, not detected. Relevant genotype: Besides indicated alterations of MnmH at position 67 encoded from the relevant mnmH gene located on the chromosome, all strains contain zbb-2558::Tn10dTc (close to mnmH), hisO1242, hisD10122 (CCC-CAA; +1 frameshift mutation), zdd-2532::Cat. Frameshifting (FS) of the indicated strains were monitored as growth of single cells on plates without histidine after 4 days at 37°C (+++, large colonies; ++, medium size colonies, +, small size colonies and (+), very small colonies). Wild type shows no growth under the same conditions. The frameshift phenotype is caused by shortage of Gln- (cmnm5s2U) due to the formation of cmnm5ges2U34 of this tRNA. This inhibition of the glutaminylation reaction causes lower levels of charged non-geranylated Gln- which in turn induces the frameshifting activity [10]. Geranylated compounds were determined by HPLC analysis of tRNA from the indicated strains.